Apparatus and method for aspirating and dispensing liquid

ABSTRACT

A liquid aspirating and dispensing apparatus and method of using the apparatus. Among other elements, the apparatus includes a liquid handling device having one or more channel members, each of which has a removable liquid holding tip attached, and a signal transmitting device. A signal transmitted from the signal transmitting device may be used in a variety of ways to yield information regarding the performance of the apparatus. This information may be provided via direct detection of the signal by an operator of the apparatus. Alternatively, the signal may be detected by a programmable signal detecting device, interpreted by the apparatus, and then displayed in a form that is understandable to the operator. Furthermore, the liquid holding tip may be modified to enable different forms of signal transmission.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the priority benefit of U.S. provisionalpatent application Ser. No. 60/788,849, filed Apr. 3, 2006, entitled“APPARATUS AND METHOD FOR ASPIRATING AND DISPENSING LIQUID” of the samenamed inventors. The entire contents of that prior application areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and method to aspirate anddispense precise volumes of liquid, and more specifically to anapparatus and method to report a variety of types of informationregarding apparatus performance or usage. The apparatus includes asignal transmitting device and an optional signal detecting device.

2. Description of the Prior Art

Many analysis methods used in biological, biotechnological,pharmaceutical, chemical and other types of research laboratoriesrequire accurate measurement and dispensing of small volumes of liquidsthat can range from one nanoliter to several milliliters. In oneapplication, small volumes of liquid may be aspirated or dispensed fromliquid handling devices having a single delivery channel or multiplechannels configured to deliver or aspirate liquid simultaneously orsequentially. Specific examples include handheld single- ormulti-channel pipettes, configured to deliver or aspirate liquid samplesfrom 1, 8 or 12 channels at a time, and automated delivery equipmentconfigured to deliver or aspirate 96 or 384 liquid samples at one time.

In general, liquid handling devices, which also may be called pipettes,are syringes, each including a cylinder extended by a shaft or channel,and a liquid holding tip and a piston to slide within the cylinder. Thepiston may be activated manually or automatically by a motor over aselectable travel distance. The travel distance may be regulatedmanually or automatically using a computer. The use of liquid handlingdevices to aspirate and dispense precise volumes of liquids is wellknown. Also well known is the use of replaceable disposable tips topermit the sequential use of such devices in the handling of differentliquids without contamination.

Replaceable tips are commonly formed from plastic and are a hollow,conical frustum with two open ends, one for mating with the shaft of theliquid handling device, and the other to permit liquid flow into and outof the interior of the tip.

For liquid handling devices, the level of aspiration and/or deliverymust be both accurate and precise. At any given time the handling devicemay not be functioning within the requirements of the process or thespecifications of the manufacturer. Many factors contribute toinaccuracy and imprecision of the liquid delivery and aspiration. Forthis reason it is necessary to repeat exactly procedures from onedelivery and/or aspiration to the next to ensure correct operation andthe integrity of the analysis. Therefore, the manufacturer must assurethat the device functions correctly at the time of the analysis.

When using an air-displacement pipette specifically to aspirate liquidfor quantitative delivery, it is important that the operator insert thetip to the correct depth in the liquid from which the aliquot is to betaken. An analysis of the importance of holding the tip at a properdepth within a liquid sample prior to aspiration is provided inInternational Organization for Standardization (ISO) standard, ISO8655-2, dated 10 Oct. 2002. Additionally, under ISO standard 8655-6,dated 10 Oct. 2002, a typical tip insertion depth for aspiration shouldbe 2-3 mm. Both ISO 8655-2 and ISO 8655-6 are incorporated herein byreference. Depending on the ambient light, on the angle of observation,on the optical density of the liquid being aspirated, and on the skilland visual acuity of the operator, this degree of accuracy can bedifficult or impossible to achieve. If the insertion depth is incorrect,then the amount of liquid aspirated by the pipette will be incorrect.According to ISO 8655-2, the error in aspirated volume due to improperinsertion depth can be up to 1%, well outside of the manufacturer'sspecified tolerance of many pipettes, typically less than 0.5%. Ittherefore would be desirable to develop a pipette and associateddisposable tip that provide a visual aid to permit an operator toclearly see when the tip is inserted to the correct depth in the sourceliquid.

The same concerns apply to liquid aspiration by an automated (robotic)liquid handling device. With automated liquid handling devices, thefunction of sensing the correct insertion depth optimally is performedby a feedback sensor. The feedback sensor provides a signal to a controlmechanism, which then directs the automated device to lower the tipuntil it is immersed to the correct depth. Where liquid aliquots aretaken repeatedly from the same source vessel, the tip also must berepeatedly inserted more deeply into the vessel after each aspirationand before the next to maintain the correct insertion depth. Aninsertion-depth detection mechanism will accomplish this automaticallyto allow more accurate and reproducible liquid delivery by the automatedliquid handler.

Another specific concern regarding the performance of liquid handlingdevices is the correct dispensing of liquid from the tip into thereceiving vessel. If the tip is situated above the surface of liquid inthe receiving vessel when liquid is dispensed (free-air or drydispense), then surface tension of the liquid in the tip will oftenprevent all of the liquid from being discharged out of the tip. If thetip is held too deeply into the liquid in the receiving vessel(wet-dispense), then liquid may adhere to the outside of the tip and beinadvertently carried out when the tip is withdrawn. Finally, if anextra measure of air is dispensed to “blow out” any residue of liquidfrom within the tip, that air can form a bubble inside the liquid in thereceiving vessel. Such bubbles generally aggregate on the side or bottomof the receiving vessel. Such a bubble is likely to lead to error whenmaking an optical absorbance or emission reading. This latter effectespecially is a problem when liquid is being dispensed into a microtiterplate because of the sample size and relative proportionate size of thebubble. Prior to dispensing an aliquot therefore, an automated liquidhandler preferably should lower the tip until it touches, or is justbelow the surface of, the liquid in the receiving vessel.

What is needed therefore is a liquid handling device including one ormore apparatus capable of detecting one or more of a multiplicity ofparameters. These parameters include: (1) whether a tip is properlyattached to a particular channel of the liquid handler; (2) that theproper type of tip is connected to the liquid handler; (3) the point atwhich the tip contacts the liquid surface, both when it is empty, foraspiration purposes, and when it is full, for dispensing purposes; (4)the point at which the tip's immersion depth in a liquid is proper,within an acceptable range for the particular pipette and tip design;(5) that liquid is present in the tip, after it has been withdrawn fromthe source vessel, to verify that aspiration has successfully takenplace; and (6) that residual liquid is not present in the tip afterdispensation is complete and after the tip is withdrawn from thereceiving vessel, to verify that dispensation has successfully takenplace.

SUMMARY OF THE INVENTION

The present invention is an apparatus and method that may be used tooptimally aspirate and dispense precise volumes of liquid. Morespecifically, the invention is an apparatus which may be used in wholeor in part to carry out a method for ensuring that the apparatus isoptimally arranged to aspirate and/or dispense precise volumes ofliquid.

The apparatus of the present invention includes a liquid handling devicehaving a channel member. A liquid holding tip is connected to thechannel member. Optimal aspiration of a liquid aliquot into the liquidholding tip and optimal dispensing of the liquid aliquot from the liquidholding tip requires that the liquid holding tip be of the proper type,and also requires that the liquid holding tip be properly arranged withrespect to both its connection to the channel member and its positionrelative to a target such as a liquid sample from which the aliquot isto be aspirated or the vessel into which the aliquot is to be dispensed.

The apparatus of the present invention further includes a lighttransmitting device, and optionally, a light detecting device. Thesedevices specifically may be used to ensure that the liquid holding tipis properly arranged for aspirating and/or dispensing.

The method of the present invention initially involves transmitting alight signal from the light transmitting device. The light signal thentravels in any one of a variety of pathways. Specifically, in thesepathways, the light travels within one or more media: air, a wall of theliquid holding tip, and optical fibers that are associated with the wallof the liquid holding tip. The light's travel in the pathway ends withthe light being detected by the light detecting device or by the humanoperator of the apparatus. The detected light signal provides theapparatus or the operator with specific information regarding the liquidholding tip, such as whether it is of the proper type, whether it isproperly connected to the channel member, or whether it is properlypositioned with respect to a target. Based on this information, theoperator may manually arrange the apparatus, or the apparatus mayautomatically arrange itself, to optimally aspirate and/or dispense thealiquot.

In an alternative embodiment of the apparatus, the liquid holding tip ismodified to include one or more mechanisms for changing the travel oflight within the tip. These light travel changing mechanisms provideinformation regarding tip selection, connection and/or positioning thatis in an alternative form available when such mechanisms are omittedfrom the apparatus.

In general, the present invention is an apparatus for aspirating liquidfrom a target sample reservoir and dispensing the liquid to a targetvessel. The apparatus includes a liquid handling device with a channelmember, a liquid holding tip removably connectable to the channelmember, and a signal transmitting device removably connectable orintegral to either or both of the channel member and the tip, whereinthe signal transmitting device is capable of transmitting an observablesignal to the target as an indication of the position of the tip withrespect to the target. Additionally, the present invention is a methodfor aspirating and dispensing liquids through a liquid holding tip fromor to a target, the liquid holding tip forming a replaceable part of aliquid handling device. The method includes the steps of positioning thetip above or in the target, transmitting an observable signal from asignal transmitting device to the target, wherein the observable signalincludes one or more indicia of position of the tip with respect to thetarget, detecting the signal, and determining from the detected signalone or more of: (1) whether the tip is properly attached to the liquidhandling device; (2) that the proper type of tip is connected to theliquid handling device; (3) the point at which the tip contacts thesurface of the liquid sample, both when the tip is empty for aspirationand when the tip contains a liquid aliquot for dispensation; (4) thepoint at which the position of the tip with respect to the target isacceptable; (5) that the liquid aliquot is present in the tip; and (6)that the aliquot or residual liquid is not present in the tip.

The details of one or more examples related to the invention are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the invention will be apparent fromthe description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of the apparatus of the presentinvention.

FIG. 2 is a longitudinal partial cross-sectional view of a simplifiedrepresentation of a first embodiment of the apparatus of FIG. 1, showingan abbreviated form of the channel member and a simple view of thedisplay panel.

FIG. 3 is a transverse cross-sectional view of the channel-tip interfaceof the embodiment of the apparatus of FIG. 2, showing a plurality ofpoint sources and point detectors.

FIG. 4 is a transverse cross-sectional view of the channel-tip interfaceof a second embodiment of the apparatus of the present invention,showing a plurality of point sources and point detectors and two annularsources.

FIG. 5 is a perspective view from below of the second embodiment of theapparatus shown in FIG. 4 without the tip attached.

FIG. 6 is a perspective view from below of the second embodiment of theapparatus shown in FIG. 4 with the tip attached.

FIG. 7 is a perspective view from below of the second embodiment of theapparatus shown in FIG. 4 without the tip attached and showing asimplified representation within the liquid handling device of theelectrical connections between the light source and detectors and thelogic circuitry, wherein the LED light sources and the light detectorsare positioned at the channel-tip interface.

FIG. 8 is a perspective view from below of the second embodiment of theapparatus shown in FIG. 4 without the tip attached and showing asimplified representation within the liquid handling device of theelectrical connections between the light source and detectors and thelogic circuitry, wherein the LED light sources and the light detectorsare positioned remote from the channel-tip interface within the channelmember.

FIG. 9 is a longitudinal view of a tip of the present invention with alight-transmitting fiber within the lumen of the tip and alight-transmitting fiber on the exterior of the tip.

FIG. 10 is a top cross-sectional view of the tip of FIG. 9.

FIG. 11 is a close-up longitudinal cross-sectional view of a tip of thepresent invention including light transmission within the tip wall andan out-coupling device, showing light scatter from the out-couplingdevice and a detector positioned at the channel-tip interface.

FIG. 12 is a simplified block representation of the primary steps of amethod of aspirating and dispensing a liquid aliquot with the apparatusof the present invention.

FIG. 13 is a side view of a first embodiment of the apparatus as it isbeing positioned to aspirate a liquid from a source.

FIG. 14 is a side view of a second embodiment of the apparatus as it ispositioned within a source of a liquid being aspirated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention is an apparatus and method for aspirating anddispensing precise volumes of liquid. As shown in FIG. 1, the apparatus10 includes among other components a liquid handling device 100 having achannel member 110 and a liquid holding tip 200, or simply, a tip 200.

The liquid handling device 100 of the apparatus 10 may be any of theliquid handling devices used by those ordinarily skilled in the art. Ittherefore is to be understood that the liquid handling device 100 mayinclude one channel member 110 or may have a plurality of channelmembers 110, and that regardless of the number of channel members 110that are included, each channel member 110 has its own tip 200. Further,the liquid handling device 100 may be operated manually orautomatically.

It also is to be understood that the tip 200 preferably is removablyconnected to the channel member 110, but it may be integral with, andtherefore undetachable from, the channel member 110.

Also as shown in FIG. 2, the apparatus 10 further includes a signaltransmitting device 120, and optionally includes a signal detectingdevice 140. The apparatus 10 preferably includes a light transmittingdevice as the signal transmitting device 120, and a light detectingdevice as the signal detecting device 140. Hereinafter, therefore, thesignal transmitting device 120 specifically will be referred to as beingthe light transmitting device 120, and the signal detecting device 140specifically will be referred to as being the light detecting device140. The apparatus 10 includes logic circuitry 160 connectable to thelight transmitting device 120, the light detecting device 140, if any,and a display device 150, if any. The display device 150 may be used todisplay information associated with the use and/or operation of theapparatus 10.

It is to be understood that the light transmitting device 120 and/or thelight detecting device 140 may be connected to or integral to the liquidhandling device 100 or either or both may not be connected to the liquidhandling device 100. It is also to be understood that the apparatus 10may include more than one light transmitting device 120 and/or one ormore light detecting devices 140, as shown in subsequent drawings.Exemplary devices that may be used as the light transmitting device 120include light emitting diodes (LEDs) or solid state diode lasers. LEDsand diode lasers are both commonly manufactured components availablefrom a number of sources including, for example, Hamamatsu Photonics ofHamamatsu City, Japan, or Bridgewater, N.J. When the signal is intendedto be viewed by the user, an LED or diode laser with a center wavelengthin the visible region of the electromagnetic spectrum (˜400-700 nm) willbe chosen. If no human viewing is required and signal processing isperformed by the logic circuitry 160, a wavelength in the visible regionor the near-infrared region (NIR, beyond ˜700 nm) can be selected.Either is suitable for the purpose of the present invention. Exemplarydevices that may be used as the light detecting device 140 include lightdetecting silicon photodiodes. Silicon photodiodes are also availablefrom a variety of sources including but not limited to the Hamamatsusource identified herein.

The apparatus 10 is configured in one or more of several ways to enablean operator to aspirate and/or dispense precise volumes of liquid bygenerating information regarding its own performance. Either the humanoperator of the apparatus 10, or where the apparatus 10 is automated,the apparatus 10 itself, may then use this information as a basis toadjust the apparatus 10 to perform optimally.

Information regarding apparatus 10 performance may be, but is notlimited to being, one or more of the following: (1) that the tip 200 isproperly attached to the channel member 110; (2) that the proper type oftip 200 is connected to the channel member 110; (3) the point at whichthe tip 200 contacts the surface of a liquid sample, both when the tip200 is empty, for aspiration purposes, and when the tip 200 is holding aliquid aliquot, for dispensing purposes; (4) the point at which theimmersion depth of the tip 200 in a liquid sample is proper, that is,when the tip 200 is immersed within the liquid to an extent which iswithin an acceptable range for the particular liquid handling device 100and tip 200 used; (5) that a liquid aliquot is present in the tip 200,such as after the liquid aliquot has been withdrawn from a liquid sampleto verify that aspiration has successfully been completed; and/or (6)that residual liquid is not present in the tip 200, such as afterdispensation is complete and after the tip 200 is withdrawn from aliquid sample to verify that dispensing has been completed successfully.

To provide these and other types of information, the apparatus 10 iscapable of being used according to one or more of a plurality ofmethods, which, in the aggregate, require that the apparatus 10 beconfigured in one or more of a plurality of ways. The exact nature ofthe information provided specifically depends upon the method, andtherefore, the configuration, used. A primary method of using andconfiguring the apparatus 10 of the present invention and severalvariations in one or more of the primary steps associated with themethod are described herein.

In all methods of using the apparatus 10, there is at least onepositioning step, at least one light transmission step, at least onelight detection step and at least one information reporting step.Further, in some, but not in all, methods of using the apparatus 10, theat least one light detection step and the at least one reporting stepmay be performed substantially simultaneously.

In the light transmission step, light is transmitted from the lighttransmitting device 120 and travels within one or more of three media:air, an optical light fiber, and the tip 200 itself. Further, during thetransmission step, the light follows a specific pathway before beingdetected in the detection step, either by the human operator of theapparatus 10 or by the light detecting device 140.

A first embodiment of the present invention is shown in transversecross-sectional view at an interface of the channel member 110 and thetip 200 as apparatus 11 in FIG. 3. The apparatus 11 includes the liquidhandling device 100 having the channel member 110 and location 250 wherethe tip 200 (not shown in this figure) engages the channel member 110.The apparatus 11 further includes a plurality of light transmittingdevices 120 and a plurality of light detecting devices 140, integrallyor removably affixed to an apparatus interior at or near channel-tipinterface 112. Specifically, the light transmitting devices 120 areaffixed to an interior wall 114 of the channel member 110 at theinterface 112. The light detecting devices 140 are similarly affixed tothe channel member 110. The light transmitting devices 120 are arrangedwithin the apparatus interior to transmit light within air external tothe tip 200. In a first alternative arrangement, the light transmittingdevice 120 is affixed to the liquid handling device 100 within thechannel member 110 above the interface 112. In a second alternativearrangement, the light transmitting device 120 is affixed within the tip200 below the interface 112. In a third alternative arrangement, thelight transmitting device 120 is affixed to a wall 240 (not shown inthis figure) of the tip 200.

A second embodiment of the present invention is shown as apparatus 12 inFIGS. 4 and 5. The apparatus 12 includes the liquid handling device 100having the channel member 110 and location 250 where the tip 200 (notshown in these figures) engages the channel member 110. The apparatus 12further includes a plurality of external light transmitting devices 120affixed to the channel member 110 at channel-tip interface 112 externalto where the tip 200 is joined to the channel member 110. The apparatus12 also includes a plurality of external light detecting devices 140affixed to the channel member 110 at the channel-tip interface 112external to where the tip is joined to the channel member 110. The lighttransmitting devices 120 transmit light within air external to the tip200 and light detecting devices 140 detect light observable in airexternal to the tip 200.

With continuing reference to FIGS. 4 and 5, the apparatus 12 includes aplurality of internal light transmitting devices 121 affixed to thechannel member 110 at channel-tip interface 112 internal to where thetip 200 is joined to the channel member 110. The apparatus 12 alsoincludes a plurality of internal light detecting devices 141 affixed tothe channel member 110 at the channel-tip interface 112 internal towhere the tip 200 is joined to the channel member 110. The lighttransmitting devices 120 transmit light within air internal to the tip200 and light detecting devices 140 detect light observable in airinternal to the tip 200. The light transmitting devices 121 and thelight detecting devices 141 may be used to determine whether an aliquotof liquid or residual liquid is located within the tip 200.

Further, the apparatus 12, includes external light transmitting device122. The light transmitting device 122 transmits light in a selectableshape, such as an annulus based on the annular shape of lighttransmitting device 122 shown in the figure, within air external to thetip 200. The apparatus 12 also includes integral light transmittingdevice 123, which is arranged to transmit light within wall 240 of thetip 200. FIG. 6 shows the light transmitting devices, including theintegral light transmitting device 123 as part of the apparatus 12 withthe tip 200 attached. The integral light transmitting device 123 isspecifically aligned to transmit light within wall 240 of the tip 200 toa target, such as a liquid sample 310 as shown in FIG. 1. In thisarrangement, the wall 240 of the tip 200 serves as an optical waveguide,in which the light travels within the wall 240 until exiting through end253. The angle of reflection internal to the body of the tip 200 must begreater than a critical angle given by Snell's Law according to theformula:

${{\sin\;\alpha_{c}} = \frac{n_{o}}{n_{i}}};$where α_(c) is the critical angle, n_(i) is the index of refraction ofthe material of which the tip 200 is constructed, and n_(o) is the indexof refraction of the media (air or sample solution) adjacent to the tipwall 240.

Proper light propagation within the wall 240 of the tip 200 alsorequires the tip 200 to be constructed of a transparentwaveguide-quality material. An exemplary material from which the tip 200may be formed is polymethylpentene. Polymethylpentene is highlytransparent and is exceptionally resistant both to chemicals and towetting. Although polymethylpentene is a preferred material, it is to beunderstood that the tip 200 is not limited, however, to being formedfrom polymethylpentene.

As illustrated in FIG. 7, the light transmitting devices, such as lighttransmitting devices 120, and the light detecting devices, such as lightdetecting devices 140, may be positioned at or near the channel-tipinterface 112. The light transmitting devices 120 are coupled to thelogic circuitry 160 including a light generator 162 through transmitter164 and leads 166. Additionally, light transmitting device 123 and/orlight transmitting device 122 may be coupled directly to the lightgenerator 162 through optical fiber 290.

As illustrated in FIG. 8, the light transmitting devices, such as lighttransmitting devices 120, and the light detecting devices, such as lightdetecting devices 140, may be positioned away from the channel-tipinterface 112. They are preferably spaced away from the tip 200 (notshown in this figure) so as to minimize heating of the liquid sample orair within the tip lumen. The light transmitting devices 120 are coupledto the logic circuitry 160 and the light generator 162 through leads166. However, the channel-tip interface includes light transmittingports 125 and light detecting ports 145 for transmitting and detectinglight. The light is transmitted through optical fibers 290 and detectedthrough optical fibers 291. Additionally, light transmitting device 123and/or light transmitting device 122 may be coupled directly to thelight generator 162 through optical fiber 290.

The tip 200 of the invention as described with respect to FIG. 6 andrelated figures may be any type of conventional tip known for use inliquid handling devices. An alternative tip arrangement may be used inthe apparatus 10 of the present invention. Specifically, as illustratedin FIGS. 9 and 10, tip 201 includes one or more of the optical fibers290 adjacent to tip wall 241. The optical fiber 290 is represented astwo separate fibers in FIGS. 9 and 10, wherein fiber 290 a extends alongthe exterior surface 242 of the tip 201 and fiber 290 b extends alongthe wall within the lumen 243 of the tip 201. The optical fibers 290a/290 b may be integrally affixed to tip wall 241, the optical fibers290 a/290 b may form an integral part of the tip wall 241, and they mayextend through to tip end 253. The optical fibers 290 may alsoalternatively be attached to the tip wall 241 rather than integrallyaffixed to or forming part thereof. The optical fibers 290 a/290 bfunction as light waveguides, thereby eliminating the need to fabricatethe tip 201 of a light transmitting material. For example, the tip 201may be fabricated of polypropylene. That is, when the present inventionincludes the use of one or more optical fibers 290 a/290 b, it is notnecessary for the tip 201 to carry a light signal, thereby eliminatingthe need to fabricate all or a portion of the tip 201 ofwaveguide-quality material.

A second alternative embodiment of the tip of the invention is a tipincluding any one or more of a plurality of out-coupling mechanisms.FIG. 11 shows one example of a portion of a tip 202 including anout-coupling mechanism 260. The tip 202 may be of the type capable oftransmitting light through tip wall 240, in the form of a lightwaveguide to pass light 130 from an integral light transmitting device123 within the tip wall 240. In the arrangement of the tip 202 shown,the out-coupling mechanism 260 includes one or more dispersion elementswhich are used to out-couple the light 130 propagating within the tipwall 240 and to establish the direction that the out-coupled light willtravel upon exiting the tip wall 240. See, for example, out-coupledlight pathways 270, which out-coupled light may be detected by lightdetecting device 140. Exemplary dispersion elements are diffractiongratings formed as parallel grooves that are substantially equallyspaced in a defined period, the grating period further defining thedirection in which light will exit the walls of the tip. Exemplarydiffraction gratings include those created by holographic processes andreplica grating formation processes, as well as others known to thosewith skill in the art of diffraction grating formation. Alternatively,the out-coupling mechanism 260 may be a scattering element such asscattering particles positioned in the tip wall 240, a roughened surfaceor area of the tip 202, or a refractive element, such as a change in thegeometry of the wall of the tip 202. It should be understood that anyarrangement for scattering the light may be employed and that thescattering element is not limited to the three examples listed. (It isalso to be understood that the optical fibers 290/291 may include anyone or more of the described out-coupling mechanisms. When the opticalfibers 290/291 include one or more of these out-coupling mechanisms, theincluded out-coupling mechanisms function in the same manner asdescribed above.)

Light 130 transmitted at the transmission step ultimately must bedetected at the detection step. Detection of the light 130 may be madesolely by the operator of the apparatus 10, solely by the lightdetecting device 140, or by both the operator and the light detectingdevice 140.

Light 130 detected solely by the operator may provide the operator withspecific information regarding apparatus 10 performance, which theoperator then may use as a basis to manually adjust the apparatus 10 sothat it performs optimally. For example, based on direct observation ofthe light 130, the operator may determine that a tip is in some waydefective, and accordingly, remove that tip and replace it with anothertip. Whenever only the operator detects the light 130, the signaldetection step and the information reporting step of the methodpreviously described are essentially performed at the same time.

Whenever a light detecting device 140 is used to detect light 130, logiccircuitry 160 connected to the light detecting device 140 processes rawdata regarding the light 130 detected, such as the change in signalintensity that occurs when the end of the tip contacts the liquid, intospecific information regarding apparatus 10 performance. For example,the logic circuitry 160 may use the raw data corresponding to a changein light intensity upon contact of the tip 200 with liquid as detectedby the light detecting device 140 to determine that the tip 200 is at aparticular position. More specifically, when the light reaches the end253 of the tip 200, some of it may be redirected (commonly done withfiber optics) back towards the source end. The light detecting device140 may be used to monitor the amount of light coming back to the sourceend. The relative amount of light coming back will change when the tip200 contacts the target, which is the surface of a sample solution. Thelight detecting device 140 detects when the tip 200 has made contactwith the sample. The logic circuitry 160 then provides the operator withinformation dictating how far the tip is to be inserted into the sample.

Information regarding performance of the apparatus 10 processed by thelogic circuitry 160 may be used in a variety of ways. In one of theseways, the information may be reported by the apparatus 10 to itsoperator in a form understandable to the operator. Specifically, thisreporting to the operator may be done by using the light transmittingdevice 120 and/or the display device 150.

Reporting of performance information by the apparatus 10 to the operatorvia the display device 150, for example, may be accomplished as shown inFIG. 2. In FIG. 2, the display device 150 is preferably a liquid crystaldisplay (LCD) that is capable of displaying one or more icons 155.However, it is to be understood that the display device 150 is notlimited to being an LCD. A light emitting diode (LED) display would notbe useful for displaying icons, but different colored LEDs in an arraywould be useful for signaling binary conditions such as success or errorconditions.

Where an LCD is used as the display device 150, the exact nature of theone or more icons 155 appearing on the LCD provides the operator withspecific information regarding the apparatus 10. The one or more icons155 therefore may indicate one or more performance indicia of apparatusstatus. For example, consider a case in which a liquid handling device100 having twelve of the channel members 110 is being used, and theapparatus 10 determines that both the third and eleventh channel membersare not ready for use. For example, they may have no tip, the wrong tip,an incorrectly connected tip, or an improperly positioned tip withrespect to a target. The logic circuitry 160 might then direct the LCDto display the numbers “3” and “11” for the purpose of reporting theirimproper status to the operator. Furthermore, more specific informationalso may be included about channel members “3” and “11.” For example,the “3” may appear and disappear intermittently, such as for reportingthat there is no tip 200 connected to channel member “3.” As anotherexample, the “11” may appear crossed out, such as for reporting that thetip 200 connected to channel member “11” is of an improper type.

Referring to a prior example, whenever the tip 200 is too far removedfrom the target, the display device 150 might display a particular icon155 that generally represents that it is not at the desired position.Further, the display device 150 might display an icon 155 that providesmore specific information, such as that the tip 200 is a specificdistance too far removed from the target.

Alternatively, information gleaned from the light 130 by the apparatus10 may be used by the apparatus 10 as a basis for automaticallyadjusting the performance of the apparatus 10. For example, theapparatus 10 may determine, based on the information detected, that atip 200 is not properly positioned with respect to a liquid sample forthe purpose of aspirating or dispensing a liquid aliquot, andaccordingly, move the tip 200 into proper position without the aid ofthe operator.

Further, the light transmitting device 120 alone may be used to reportinformation interpreted by the logic circuitry 160 to the operator.Specifically, light may be transmitted in a variety of manners by thelight transmitting device 120, with each manner representing aparticular type of information. For example, the light may betransmitted by modulating intensity and/or wavelength. For example, atip 200 determined by the apparatus 10 to have an unacceptable statusmay illuminate, whereas a tip 200 having a desired status may fail toilluminate, or vice versa. As another example, an improperly arrangedtip 200 may repeatedly cycle through periods of illumination andnon-illumination, while a properly arranged tip 200 may remaincontinuously illuminated or non-illuminated, or vice versa. As yetanother example, an improperly arranged tip 200 may illuminate as onecolor, such as red, and a properly arranged tip 200 may illuminate asanother color, such as green.

The apparatus 10 of the present invention and one or more of thevariants described herein may be used to perform a liquid aspiration anddispensation method 500 including a plurality of primary steps asrepresented in FIG. 12. The method 500 includes additional and optionalsteps to be described herein. Initially, and with reference to FIGS. 12and 13, a first step 501 involves selecting a removably affixable tip200 for attachment to a channel member 110 of a liquid handling device100 as previously described. The channel member 110 includes one or morelight transmitting devices 120 affixed thereto. The channel member 110also includes one or more light detecting devices 140 affixed thereto.The tip 200 is affixed to the channel member 110 at interface 112,either by reversibly screwing it on, or by creating a friction fit orany of the other methods familiar to those skilled in the art.

The step of selecting a tip 501 includes the step of connecting the tip200 to the channel member 110. The method 500 may include optional step502 of determining whether the tip 200 selected is the type suitable forthe intended purpose and optional step 504 of determining whether anaffixed tip is properly connected to the channel 110. For this step, thetip of FIG. 11 may be used, wherein the integral light transmittingdevice 123 is arranged to enable light transmission within the tip wall240, wherein the tip wall 240 includes the out-coupling mechanism 260.Light 130 is transmitted within the tip wall 240 by the integral lighttransmitting device 123 to exit the tip wall 240 through theout-coupling mechanism 260 where it is then detected by the lightdetecting device 140. For example, the light detecting device 140 may bepositioned on the apparatus 10 such that it will detect selectableout-coupled light from the tip. A particular light detecting device maybe configured and arranged to detect light of certain characteristics.That light of certain characteristic may correspond to an out-coupledportion of light transmitted through the tip wall 240, whichout-coupling is the result of the positioning of an out-couplingmechanism grating. A second light detecting device may be positioned onthe apparatus to detect out-coupled light produced through a secondout-coupling mechanism grating physically spaced from the first grating.Alternatively, the second out-coupling mechanism may simply generate adifferent detectable light out-coupling from the tip. The detected lightinformation from the light detecting devices may be used by the logiccircuitry 160 to determine proper tip selection and attachment. Thelogic circuitry 160 may then direct the display device 150 to reportthat the proper tip is properly connected to the channel member 110according to any one or more of the variety of ways described before. Aplurality of out-coupling light mechanisms may also be employed todetermine whether the tip has been immersed to a suitable depth within asample.

It is to be noted that the present invention takes advantage of theconcept of light back-reflection, which is the propagation of light backtoward its origin. The invention is capable of detecting light signalchanges that occur at the interface between two media having differentrefractive indices, which is either the interface between the tip 200and air or between the tip 200 and liquid. Specifically, in regard tothe present invention, light travels to the end 253 of the tip 200, theend 253 being defined as the interface between the medium of tip 200 andthe opposing medium, which is either air or liquid. As the lightintersects the end 253 of the tip 200, a portion of the light will bereflected by the interface, while the remaining portion will berefracted across the interface. The refracted portion of the light willcross the interface between the tip 200 medium and the opposing medium(either air or liquid), thereby escaping the tip 200 medium, and willcontinue to travel away from the tip 200 through the opposing medium(either air or liquid). The reflected portion of the light will bedirected back toward its origin, and will propagate back through the tip200, which effect is commonly referred to as “back-reflection”. Therelative proportion of the light that will be back-reflected at the end253 of tip 200 is defined by the reflectivity coefficient R:

${R_{1,2} = \left( \frac{\eta_{1} - \eta_{2}}{\eta_{1} + \eta_{2}} \right)^{2}};$where, in the context of the present invention, R_(1,2) is thepercentage of light reflected at the interface between the tip 200medium and the opposing medium (either air or liquid), and η₁ and η₂ arethe angular dependent refractive indices of the tip 200 medium and theopposing medium (either air or liquid), respectively. This equationdemonstrates that the amount of light reflected at any interface betweentwo different media, such as, for example, the tip medium 200 and theopposing medium, is dependent upon the refractive indices of thosemedia. Because the tip 200 medium and the opposing medium have differentrefractive indices, a portion of the incident light is reflected backinto the tip 200 at the interface between the end 253 and the opposingmedium. This reflected light may be used, for example, to determine thatthe end 253 is touching the surface of the sample 310 or is immersed inthe sample 310. This is true because the intensity of the light that isback-reflected into the tip 200 will change, as detectable by the lightdetecting device 140, whenever the end 253 leaves air and contacts theliquid sample 310 due to the difference in refractive indices betweenthe air and the liquid sample 310. The optical fibers 290/291 may besubstituted for the tip 200 to achieve this same result as they may beused in the process of detecting light signal changes.

Upon confirming that the proper tip 200 has been properly connected tothe channel member 110, the step 506 of positioning the tip 200 toobtain an aliquot of liquid is performed by moving the tip 200 of theliquid handling apparatus 100 to the liquid sample 310. The liquidsample 310 may be contained in a vessel such as a well of a multiwellplate or a test tube. The liquid sample 310 is a target for the light130 transmitted by the light transmitting device 120. Prior topositioning the tip 200 for aspiration, the method 500 includes theoptional step 505 of ensuring that there is no residual liquid in thetip 200. With reference to FIG. 14, this may be achieved by transmittinglight 130 from one or more light transmitting devices 121 positioned totransmit light within the tip 200. If there is residual liquid presentin the tip 200, the pathway of transmitted light is changed and thechange detected by the light detecting device 141. Upon receivinginformation of the detected change, the logic circuitry 160 may theninstruct the display device 150 to report that residual liquid ispresent in the tip 200 according to any one or more of the variety ofways described hereinabove. If there is no residual liquid within thetip 200, no light is reflected to the light detecting device 141. Uponfailing to detect light, the logic circuitry 160 may instruct thedisplay device 150 to report that the tip 200 is clear and ready foraspiration.

The step 506 of positioning includes aligning the tip 200 properly overthe sample 310. As shown in FIG. 13, that may be achieved by observinglight marks 316 on the surface 315 of the sample 310. If the light marks316 are not aligned, such as shown in the figure, then the tip 200 isnot properly positioned. The step 506 also includes the step of properlyimmersing the tip 200 within the liquid sample 310. This may beperformed automatically by the apparatus or manually by the operator.Initially, the tip 200 is held at some position, which may bearbitrarily chosen by the operator or an automated form of the liquidhandling device 100, within the liquid sample 310 from which the aliquotis to be aspirated, as shown in FIG. 14. Light is then transmitted fromthe light transmitting device 120 to the surface 315 of the liquidsample 310. When the light 130 strikes the surface, the surface 315becomes illuminated such that the light 130 acts as to spotlight atleast a portion the surface 315. In this arrangement, a portion of thelight 130 is reflected from the surface 315, and that light forms anunderstandable image, such as the solid circle mark 317 shown on thesurface 315. The resolution of the circle mark 317 may be variable, suchthat it may become more focused as the tip 200 reaches the appropriateposition above the surface 315 of the liquid sample 310. Alternatively,when multiple light transmitting devices 120 are used, it may be whenall circles are aligned. The light transmitting device 120 may beconfigured to ensure that the circle mark 317 is properly focused whenthe tip 200 is in optimal immersion position for aspiration, such asshown in FIG. 14. In this arrangement, the operator can achieve theoptimal immersion depth by manually adjusting the position of the tip200 within sample 310 until the operator visualizes a single circle mark317 having what is perceived to be optimal clarity or resolution.Alternatively, the optimal immersion position may be identified throughautomatic adjustment of the tip position by the liquid handling device100 when the light detecting device 140 detects the intensity of thereflected light represented by the circle mark 317 and the logiccircuitry 160 calculates that the circle marks 317 from all lighttransmitting devices 120 are aligned and/or in focus.

The next step of the method 500 of the present invention involves thestep 508 of aspirating the liquid into the tip 200 after thedetermination has been made that the tip 200 has been immersed to thedesired position. This step may be performed manually or automaticallyas is well known to those skilled in the art of liquid aspiration anddispensation. The method 500 may include the optional step 509 ofensuring that the liquid aliquot is contained in the tip 200. Withreference to FIG. 14, this may be achieved by transmitting light 130from one or more light transmitting devices 121 positioned to transmitlight within the tip 200. When a liquid aliquot 330 is present in thetip 200, transmitted light 130 is reflected from surface 331 of thealiquot 330 and is detected by the light detecting device 141. Upondetecting the light 130, the light detecting device 141, via the logiccircuitry 160, may then instruct the display device 150 and/or one ormore of the light transmitting devices 121 to report that the aliquot330 is present in the tip 200 according to any one or more of thevariety of ways described hereinabove. If there is no aliquot 330 withinthe tip 200, no light 130 is reflected to the light detecting device141. Upon failing to detect light 130, the light detecting device 141,via the logic circuitry 160, may instruct the display device 150 and/orone or more of the light transmitting devices 121 to report that the tip200 does not contain the aliquot 330.

Upon determining that the tip 200 is properly connected to the channelmember 110 and that the liquid aliquot is contained in the tip 200, themethod 500 includes step 510 of dispensing the aliquot of liquid into atarget vessel, which may be empty or which may include liquid sample310. The tip 200 is positioned above the surface of the liquid sample310 (or bottom of the vessel) for proper dispensing of the aliquot intothe liquid sample 310. The tip 200 is initially held at a selectableposition above the liquid sample 310 into which the aliquot is to bedispensed. Light 130 then is transmitted from the light transmittingdevice 120 to the surface 315 of the liquid sample 310 such that thesurface 315 becomes illuminated. In this arrangement, a portion of thelight 130 is reflected from the surface 315, which forms an image, suchas circle mark 317 on the surface 315. Upon confirming that the circlemark 317 is singular and/or of desired intensity, it is determined thatthe tip 200 is held at the optimal distance above the surface 315 foraliquot dispensing. In this arrangement, the operator can achieve theoptimal tip position above the target vessel by manually adjusting theposition of the tip 200 with respect to the liquid surface 315 until theoperator visualizes the circle mark 317 having maximum resolution. Whenit has been determined that the tip 200 is at the desired position, thealiquot within the tip 200 may be dispensed into the vessel.

In addition to assisting the operator to position the tip 200 at thepreferred location for dispensing, there is an added benefit ofemploying the light transmitting device 120. Specifically, thetransmitted light 130 allows the operator to better visualize thetarget. This enhanced visualization aids in the positioning of the tip200. Furthermore, it is particularly advantageous that the light 130 isreflected near the tip 200 because the tip 200 normally has the focus ofthe operator's attention during use of the apparatus 10.

The step of positioning for aliquot dispensing may be performed manuallyas described above, or it may be performed automatically, such as partof an automated liquid handling process. In that process, the lightdetecting device 140 and the logic circuitry 160 operate together todetect the transmitted light, determine proper tip positioning andeither report the information to an operator to complete the aliquotdispensing, or complete the dispensing step automatically. Those skilledin the art of liquid aliquot aspiration and dispensation will recognizethe steps to be completed in dispensing the aliquot from the tip afterconfirming that the tip 200 is properly positioned for dispensation.

In an alternative arrangement of the present invention, the tip 200 maybe configured with a modified region such that it glows, either byscattered light, or by the presence of some fluorescent material, whenlight is propagating inside the tip wall 240, and encounters thismodified region. The angle that the light is propagating within the tip200 is engineered so that Total Internal Reflection (TIR) is occurringwith the tip 200 in air, but not when it is immersed in solution. Whenthe tip 200 is in air, the glowing region “glows” because the lightsuccessfully propagates within the tip 200 to that point. However, whenthe tip 200 is immersed in solution, once the light reaches the solutionregion, it is no longer confined within the tip 200 because TIR nolonger occurs. At this point the light exits the tip 200. Once the tip200 has been immersed deep enough such that the glowing region isimmersed, the light will escape the tip wall 240 before it has thechance to pass into the glowing region, and that region will “turn off”and no longer glow. There would then be, in effect, two regions of thetip 200, an upper and a lower. The object is to insert to the point thatthe lower region is off, but the upper region is on.

Other variations of the examples and designs described and shown hereincan be implemented. For example, the steps of the method described maybe performed in different order. Two or more steps may be performedsimultaneously. Additionally, one or more steps of the method related toactivation of the light transmitting device 120, the light detectingdevice 140, and/or the logic circuit 160 may be implemented as acomputer program product as computer-readable signals on acomputer-readable medium. For example, the computer-readable medium maybe a non-volatile recording medium, an integrated circuit memoryelement, or a combination thereof. Such computer program product mayinclude computer-readable signals tangibly embodied on thecomputer-readable medium, where such signals define instructions, forexample, as part of one or more programs that, as a result of beingexecuted by a computer, instruct the computer to perform one or moreprocesses or acts described herein, and/or various examples, variationsand combinations thereof. Such instructions may be written in any of aplurality of programming languages, for example, Java, Visual Basic,XML, C, or C++, Fortran, Pascal, Eiffel, Basic, COBOL, and the like, orany of a variety of combinations thereof. The computer-readable mediumon which such instructions are stored may reside on one or more of acomputer device and/or the components of a computer network system.

It is to be understood that various modifications may be made to theapparatus and method without departing from the spirit and scope of theinvention.

1. An apparatus for aspirating liquid from a first target and dispensingthe liquid to a second target, the apparatus comprising: a. a liquidhandling device including one or more channel members; b. a liquidholding tip removably connectable to each one of the one or more channelmembers, wherein the liquid holding tip includes a tip wall at leastpartially including a waveguide-quality material integral with oradjacent to the tip wall; and c. one or more signal transmitting devicesremovably connectable or integral to one or more of the one or morechannel members and configured to transmit a signal within thewaveguide-quality material of the wall of the liquid-holding tip,wherein each of the one or more signal transmitting devices is capableof transmitting at least one first signal to the first target as anindication of the position of the liquid holding tip with respect to thefirst target, and wherein each of the one or more signal transmittingdevices is capable of transmitting at least one second signal to thesecond target as an indication of the position of the liquid holding tipwith respect to the second target.
 2. The apparatus of claim 1 whereinat least one of the one or more signal transmitting devices is a lighttransmitting device.
 3. The apparatus of claim 2 wherein one or both ofthe at least one first signal and the at least one second signaltransmitted by the light transmitting device acts to spotlight at leasta portion of one or both of the first target and the second target. 4.The apparatus of claim 2 wherein the light transmitting device iscapable of transmitting light in a selectable shape.
 5. The apparatus ofclaim 2 wherein the apparatus further includes one or more signaldetecting devices, wherein one or both of the at least one first signaland the at least one second signal are detectable by the one or moresignal detecting devices after either or both of the first signal andthe at least one second signal are reflected from one or both of thefirst target and the second target, and wherein at least one of the oneor more signal detecting devices is a light detecting device.
 6. Theapparatus of claim 5 further comprising logic circuitry coupled to theat least one light detecting device, wherein the at least one lightdetecting device is capable of providing to the logic circuitryinformation regarding the tip's position.
 7. The apparatus of claim 6wherein the information regarding the tip's position that the at leastone light detecting device is capable of providing to the logiccircuitry includes information to be used to re-position the tip.
 8. Theapparatus of claim 5, wherein the waveguide-quality material includesone or more optical fibers adhered adjacent to the tip, wherein the oneor more optical fibers are capable of carrying light.
 9. The apparatusof claim 8 wherein the one or more optical fibers include one or moreout-coupling devices.
 10. The apparatus of claim 9 wherein the one ormore out-coupling devices is a diffraction grating, and wherein thediffraction grating is capable of diffracting light.
 11. The apparatusof claim 9 wherein the one or more out-coupling devices is a roughenedarea on the one or more optical fibers or a change in the geometry ofthe one or more optical fibers, and wherein the roughened area or changein geometry causes the light being carried by the one or more opticalfibers to be dispersed from the one or more optical fibers.
 12. Theapparatus of claim 9 wherein at least one of the one or moreout-coupling devices includes one or more light dispersion elementscapable of establishing the direction that light carried by the one ormore optical fibers travels upon exiting the one or more optical fibers.13. The apparatus of claim 9 wherein the tip wall includes two or moreout-coupling devices arranged such that light traveling in the tip wallexits any of the two or more out-coupling devices positioned above theliquid surface, but does not exit any of the two or more out-couplingdevices immersed in the liquid, thereby indicating to the human operatorthat the proper immersion depth has been obtained.
 14. The apparatus ofclaim 8 wherein one or both of the first signal and the second signalare light, and a portion of either or both of the first signal and thesecond signal are detectable by the one or more signal detecting devicesafter being back-reflected into the one or more optical fibers adjacentto the tip wall.
 15. The apparatus of claim 1 wherein one or both of theat least one first signal and the at least one second signal arevisually detectable by a human operator.
 16. The apparatus of claim 1wherein the apparatus further includes one or more signal detectingdevices, and one or both of the at least one first signal and the atleast one second signal are detectable by the one or more signaldetecting devices after either or both of the at least one first signaland the at least one second signal interact with one or both of thefirst target and the second target.
 17. The apparatus of claim 16further comprising logic circuitry coupled to the one or more signaldetecting devices.
 18. The apparatus of claim 17 wherein the apparatusfurther includes one or more display devices, wherein the logiccircuitry is coupled to any of the one or more display devices, andwherein the logic circuitry is programmed to direct any of the one ormore display devices to display information about the tip.
 19. Theapparatus of claim 17 wherein the logic circuitry is coupled to the oneor more signal transmitting devices and the logic circuitry is capableof controlling the operation of the one or more signal transmittingdevices.
 20. The apparatus of claim 1 wherein one or both of the atleast first one signal and the at least one second signal is modulated.21. The apparatus of claim 1 wherein one or both of the first signal andthe second signal are light, and a portion of either or both of thefirst signal and the second signal are detectable by the one or moresignal detecting devices after being back-reflected into the interior ofthe tip wall.
 22. The apparatus of claim 1 wherein the tip wall includesone or more out-coupling devices.
 23. The apparatus of claim 22 whereinthe one or more out-coupling devices is a diffraction grating capable ofdiffracting the light carried by the tip wall.
 24. The apparatus ofclaim 22 wherein the one or more out-coupling devices is a roughenedarea on the tip wall or a change in the geometry of the tip wall, andwherein the roughened area or change in geometry is capable ofdispersing light carried by the tip wall.
 25. The apparatus of claim 22wherein at least one of the one or more out-coupling devices includesone or more light dispersion elements capable of establishing thedirection that the light carried by the tip wall travels upon exitingthe tip wall.
 26. The apparatus of claim 22 wherein the tip wallincludes two or more out-coupling devices arranged such that lighttraveling in the tip wall exits any of the two or more out-couplingdevices positioned above the liquid surface, but does not exit any ofthe two or more out-coupling devices immersed in the liquid, therebyindicating that the proper immersion depth has been obtained.